Biology 11 Name:Ms. Hansen Date:

The following lab will be completed on the ipads and the video will be uploaded to our youtube account. All blanks/questions (underlined parts) should be answered in order as you proceed through the lab, using either voiceover or text.

Purpose: In this Lab you will observe and dissect a frog in order to observe the external and internal structures of frog anatomy.

Materials: • safety goggles, gloves, and a lab apron• dissecting tray and paper towels• forceps/tweezers• dissecting pins (10)• scissors• dissecting needle• probe• ruler• preserved frog

Safety:Only 1 pair of hands in the dissecting tray at any given time!RESPECT the animal that has been provided for educational purposes!

Instructions:Part A - External anatomy

1. Place a frog on a dissection tray. To determine the frog’s gender, look at the hand digits, or fingers, on its

forelimbs. A male frog usually has thick pads on its "thumbs," as shown in the diagram below.

What do you think these pads are for? Is your frog male or female?

2. Use the diagram below to locate and identify the external features of the head. Find the mouth, external nares (nostrils), tympani (eardrums), eyes, and nictitating membrane (a clear eyelid attached to the bottom of the eye).

3. Observe the dorsal side and the ventral side of the frog. What is the difference in colour?4. Feel the frog’s skin. How does it feel?5. Examine the appendages. Measure the hindlegs and the fore limbs6. How many digits (toes) are on the hind feet? Forefeet? Are they webbed? 7. Locate the frogs eyes and use tweezers and scizzors to carefully remove the nictitating membrane. What is

the function of the nictitating membrane? (Hint: alligators and crocodiles also have this membrane) 8. Extend the probe through the nostril and see where the probe exits inside of the mouth. Why are the nostrils

located at the highest point on the frogs head?

Part B – anatomy of the frog’s mouth1. Pry the mouth open and use scissors to cut the hinges of the mouth to view the structures inside.2. Locate the tongue. Does it attach to the front or back of the mouth? Why do you think it is attached there?

Carefully remove the tongue.3. In the center of the mouth toward the back is a single round opening. This is the esophagus that leads to the

stomach. 4. Close to the angles of the jaw are two openings, one on each side. These are the Eustachian tubes. They are

used to equalize the pressure in the inner ear while the frog is swimming. Insert a probe into the Eustachian tube. To what structure does the Eustachian tube attach?

5. Just behind the tongue before you reach the esophagus is a slit like opening. (you may need to use your probe to get it to open up) This is the glottis the opening to the lungs. (identify the glottis)

6. The frog has two sets of teeth. The vomerine teeth are found on the roof of the mouth. The maxillary teeth are found around the edge of the mouth. Both are used for holding prey, frogs swallow their meals whole and do NOT chew. (identify the teeth)

7. On the roof of the mouth, you will find two tiny openings, if you put your probe into those openings, you will find they exit on the outside of the frog. These are the internal nares. (identify the nares)

8. Label the frogs mouth. Label each of the structures in Bold above.

Part C – Frog internal anatomy

Dissection Instructions 1. Place the frog in the dissecting pan ventral side up. 2. Use scissors to lift the skin and abdominal muscles away from the body

cavity. Cut along the midline of the body from the pelvic to the pectoral girdle.

3. Make transverse (horizontal) cuts near the arms and legs. 4. Lift the flaps of the body wall and pin back.

*If your specimen is a female, the body may be filled with eggs and an enlarged ovary. You may need to remove these eggs to view the organs.

Locate each of the organs below and check the box to indicate that you have found the organs. Include all of the organs in you r video Fat Bodies - Spaghetti shaped structures that have a bright orange or yellow color, if you have a particularly fat frog, these fat bodies may need to be removed to see the other structures. Usually they are located just on the inside of the abdominal wall. Peritoneum - A spider web like membrane that covers many of the organs, you may have to carefully pick it off to get a clear view

Liver - The largest structure of the body cavity. This brown colored organ is composed of three parts, or lobes. The right lobe, the left anterior lobe, and the left posterior lobe. The liver is not primarily an organ of digestion, it does secrete a digestive juice called bile. Bile is needed for the proper digestion of fats. Heart - at the top of the liver, the heart is a triangular structure. The left and right atrium can be found at the top of the heart. A single ventricle located at the bottom of the heart. The large vessel extending out from the heart is the conus arteriosis. Lungs - Locate the lungs by looking underneath and behind the heart and liver. They are two spongy organs. Gall bladder - Lift the lobes of the liver, there will be a small green sac under the liver. This is the gall bladder, which stores bile. (hint: it kind of looks like a booger)

Stomach - Curving from underneath the liver is the stomach. The stomach is the first major site of chemical digestion. Frogs swallow their meals whole. Follow the stomach to where it turns into the small intestine. The pyloric sphincter valve regulates the exit of digested food from the stomach to the small intestine. Small Intestine - Leading from the stomach. The first straight portion of the small intestine is called the duodenum, the curled portion is the ileum. The ileum is held together by a membrane called the mesentery. Note the blood vessels running through the mesentery, they will carry absorbed nutrients away from the intestine. Absorption of digested nutrients occurs in the small intestine. Large Intestine - As you follow the small intestine down, it will widen into the large intestine. The large intestine is also known as the cloaca in the frog. The cloaca is the last stop before wastes, sperm, or urine exit the frog's body. (The word "cloaca" means sewer) Spleen - Return to the folds of the mesentery, this dark red spherical object serves as a holding area for blood. Esophagus - Return to the stomach and follow it upward, where it gets smaller is the beginning of the esophagus. The esophagus is the tube that leads from the frogs mouth to the stomach. Open the frogs mouth and find the esophagus, poke your probe into it and see where it leads.

STOP! If you have not located each of the organs above, do not continue on to thenext sections!

Removal of the Stomach: Cut the stomach out of the frog and open it up. You may find what remains of the frog's last meal in there. Look at the texture of the stomach on the inside. What did you find in the stomach?

Measuring the Small intestine: Remove the small intestine from the body cavity and carefully separate the mesentery from it. Stretch the small intestine out and measure it. Now measure your frog. Urogenital System - The frog's reproductive and excretory system is combined into one system called the urogenital system.

Kidneys - flattened bean shaped organs located at the lower back of the frog, near the spine. They are often a dark color. The kidneys filter wastes from the blood.

Testes - in male frogs, these organs are located at the top of the kidneys, they are pale colored and roundish.

Oviducts - females do not have testes, though you may see a curly-q type structure around the outside of the kidney, these are the oviducts. Oviducts are where eggs are produced. Males can have structures that look similar, but serve no actual purpose. In males, they are called vestigial oviducts.

Bladder - An empty sac located at the lowest part of the body cavity. The bladder stores urine. Cloaca - mentioned again as part of the urogenital system - urine, sperm and eggs exit here.

Label the parts of the urogenital system below.

Frog male reproductive system Frog female reproductive system

Label the Diagram

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